A theoretical calculation method for critical air velocity to prevent methane draft pressure-caused airflow reversion based on oscillation theory.

Methane draft pressure is a secondary disaster for mine ventilation following coal and gas outbursts, which poses a long-term threat to coal mining and workers' safety. To study the law of methane draft pressure-caused airflow variation, oscillation theory is introduced in this study. The vibration equation is used to deduct the basic equation of airflow oscillation in parallel upward ventilated airways, which regards the entire methane and air as one vibrating object in the loop of the parallel airways. The theoretical critical air velocity to prevent airflow reversion is calculated by the airflow oscillation equation using numerical methods. Furthermore, through dimensional analysis, a formula is given to calculate the critical velocity directly. The theoretical results were compared with experiments and good agreements were obtained, which verifies the rationality of the assumptions in the theoretical deduction process. The conclusion of this study indicates that, in a short time, oscillation theory can be used to predict the critical air velocity to prevent airflow reversion, and be feasible in revealing the essence of methane draft pressure-caused airflow reversion. An airflow oscillation model is built to analyze and predict methane draft pressure-caused airflow reversion based on oscillation theory. A method is carried out to calculate the critical velocity that prevents airflow reversion based on the airflow oscillation model. The conclusions of this paper provide a theoretical basis for further understanding the essence of the airflow reversion caused by methane draft pressure. [ABSTRACT FROM AUTHOR]